Abstract: The surface tension curve of carboxylate Gemini surfactant (CGS-12) was measured using the platinum plate method. The effects of pH value, the addition of inorganic salts and alcohols on the surface properties of CGS-12 were investigated. In addition,the dynamic surface tension curve of CGS-12 was measured using drop volume method,and the dynamic adsorption mechanism was also explored. The results show that the cmc and γ_cmc of CGS-12 are 80 μmol/L and 26.37 mN/m, respectively. The adjustment of pH value of solution leads to a reversible change of the surface tension of CGS-12 which reaches the minimal at the pH value of 6. Increasing the concentration of NaCl, the surface tension of CGS-12 decreases first and then increases. However, the surface tension of CGS-12 undergoes an increase before reaching a plateau as the concentration of CaCl₂ is increased. The surface activity of CGS-12 increases with the increasing concentration of n-butanol. Increasing the carbon chain lengths of the alcohol, γ_cmc decreases significantly with no obvious variation for cmc. The results of the dynamic surface tension show that the adsorption at low concentration of CGS-12 is controlled by diffusion at the beginning and then a mixed kinetic-diffusion adsorption mechanism toward the end. At higher concentration of CGS-12, the adsorption process is controlled by the mixed kinetic-diffusion adsorption mechanism for the later stage although it can’t be simulated at the initial stage.

Key words: carboxylate Gemini surfactant, surface activity, surface tension, salt resistance, dynamic adsorption